right this is a question not a invotation for an arguemet!



now the head off my spare engine is nearly off im thinking off trying to port the whole thing by my self but want to know wether it is possible to use valves from other cars as i wan to put bigger valves in the head to accomadate my new cams that will go in it.

are 20v turbo valves bigger?

also on the net half say a polished serfice is good to stop premature detonation and the other half say it will loose me power anybody got any thoughts on this?

chears
mick

Polishing a ported head is usualy a waste of time and can cost you power/economy at lower revs.
Detonation issues are mostly an issue with controling of the ignition advance timing and it not being properly matched to a new compression ratio and/or fueling change requirements of a modded engine.

chears,

im having a go cos its a spare mate.

from what ive read though alot of people say a build up of carbon can result in detonation hence the polishing of the valve guides etc but also there are others that say it can loose me power.

well i thought id share this picture with the good guys on here (sort of a progress pic lol)


this is the head i will be using to c if i can improve on it, check out the valves lol this pic dont do it justice they were in a right mess and so were the pistons.

Just remember to post before and after dyno plots.

You dont need to polish the combustion chamber to decarbonise it or the exhaust ports.

Im currently stripping and rebuilding an engine atm too (and just finised decarbonising (de-cokeing) the head and valves.

I suggest you strip the head til all you have is the bare head and then coat (absolutly paste it on) the carbonised areas with paint stripper (i used nitromors) and then scrub it off with a tooth brush (2 for 15p at asda) and continue this process (2-3 times should do it) and you should have a clean cyliner head. to remove deposits at the end scrub the block with petrol. for really stuborn bits (and the valves) use a wire brush attachment on a dremel (or similar rotary tool), this will bring it off easy enough. dont grind your head or try to port and polish it. the best method to clean up your head and get rid of casting marks is a process called 'extrude honing'. but do not change the shape of your ports unless you have a professional to help you and a flow bench.

These are my results on decarbonising my head:-
Exhaust port (this was completly black)

Dirty and clean

Carbon in the cyl and exhaust ports helps retain heat in the gasses and makes the engine more efficient.

looks like you been bang at it mate

chuckles

Drinking the derv again Ian?

Got myself an E90 nowadays. And yes, it's diesel

Someone has too much time on their hands!

Thats bleedin awesome.

Buzz
The champion of the Bravo 1.4
& now ex owner of a Bravo 1.8

somebody close this please

chears

Donnylad, dont stress mate. The real world is crueller!

for the record, i dont have a clue about porting/polishing, and what oversize valves may or may not fit. Inside the engine is somewhere i never go unless you count oil changes, haha.

Buzz
The champion of the Bravo 1.4
& now ex owner of a Bravo 1.8

That's harsh but also well funny.

Donny if you want your head ported properly contact me, I have done a few coupe heads with results however would be interesting to do a NA head even thou the heads are exactly the same the porting will be different. What cams are you using as that is a very important factor to consider, you could do it yourself but in all honesty you WILL lose power.

Good luck